This invention relates to roof bolts.
It has already been proposed to use, as the tendon in a roof bolt, a length of square twist steel, file. A length of square steel bar twisted about its longitudinal axis. In general, the tendon of a roof bolt must have a threaded, operatively outer end that will project from the drilled hole in a rock formation to take a nut which is used to clamp a washer against the periphery of the mouth of the hole.